Skip to contentSkip to conversation

f2fs: avoid race between zero_range and background GC

PATCH New Chao Yu 1 participant 1 message Aug 5, 2018 F2FS file system

lore
Share & tools
lore

Chao Yu

author maintainer
#0 lore raw

PATCH v2 1/1 f2fs: avoid race between zero_range and background GC

From: Chao Yu <[email protected]>

Thread A Background GC
- f2fs_zero_range
- truncate_pagecache_range
- gc_data_segment
- get_read_data_page
- move_data_page
- set_page_dirty
- set_cold_data
- f2fs_do_zero_range
- dn->data_blkaddr = NEW_ADDR;
- f2fs_set_data_blkaddr

Actually, we don't need to set dirty & checked flag on the page, since all valid data in the page should be zeroed by zero_range().

Use i_gc_rwsem[WRITE] to avoid such race condition.

Signed-off-by Chao Yu <[email protected]>

---
v2:
- decrease i_gc_rwsem lock coverage.

 fs/f2fs/file.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)
fs/f2fs/file.c +9 -2
index 606c5a215542..bcffb3b608ed 100644
@@ -1311,8 +1311,6 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
 	if (ret)
 		goto out_sem;
 
-	truncate_pagecache_range(inode, offset, offset + len - 1);
-
 	pg_start = ((unsigned long long) offset) >> PAGE_SHIFT;
 	pg_end = ((unsigned long long) offset + len) >> PAGE_SHIFT;
 

@@ -1342,12 +1340,19 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
 			unsigned int end_offset;
 			pgoff_t end;
 
+			down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+
+			truncate_pagecache_range(inode,
+				(loff_t)index << PAGE_SHIFT,
+				((loff_t)pg_end << PAGE_SHIFT) - 1);
+
 			f2fs_lock_op(sbi);
 
 			set_new_dnode(&dn, inode, NULL, NULL, 0);
 			ret = f2fs_get_dnode_of_data(&dn, index, ALLOC_NODE);
 			if (ret) {
 				f2fs_unlock_op(sbi);
+				up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
 				goto out;
 			}
 

@@ -1356,7 +1361,9 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
 
 			ret = f2fs_do_zero_range(&dn, index, end);
 			f2fs_put_dnode(&dn);
+
 			f2fs_unlock_op(sbi);
+			up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
 
 			f2fs_balance_fs(sbi, dn.node_changed);
Signature · 1 line
2.18.0